CoCo serial port wiring
From Wikistix
Normally, CoCo serial TX line appears to be held low at about -10V, data bits around +10V. The BASIC output routines (LLIST, PRINT #-2, etc) check that RX is high (>0V) before proceeding - I assume this is some sort of hardware flow control. If flow control is not required, this can be held high by tying to DTR.
| Cable - CoCo DIN pin | DE-9 bi-di serial pin | DE-9 printer pin |
|---|---|---|
| 1 cd | NC | NC |
| 2 rx | 3 tx | 4 dtr |
| 3 gnd | 5 gnd | 5 gnd |
| 4 tx | 2 rx | 2 rx |
